Binh Thai Luc, 35, is accused of killing five people in San Francisco's Ingleside neighborhood on March 23, 2012. (CBS)Binh Thai Luc, 35, is accused of killing five people in San Francisco's Ingleside neighborhood on March 23, 2012. (CBS)

SAN FRANCISCO (KCBS) – A conflict of interest prevents the San Francisco Public Defender’s Office from representing the man accused of killing five people at a home near City College of San Francisco, a judge ruled Thursday.

Judge Lucy McCabe sided with prosecutors who said Public Defender Jeff Adachi’s office could not represent Binh Thai Luc because a public defender had previously represented Luc’s brother, Brian, who could be a key witness in the case.

KCBS’ Bob Melrose Reports:

Adachi argued in court Thursday morning that his office no longer represented Brian Luc once he was sentenced in his prior case.

But Chief Assistant District Attorney Sharon Woo said, “Our obligation … is to ensure Mr. Luc has conflict-free counsel, and in this case that simply can’t be the public defender.”

McCabe ended up ruling in favor of the prosecution, citing the fact that the two defendants are brothers and lived at the same address.

Binh Luc made his initial appearance in court on Wednesday when Adachi argued that his office should be allowed to represent Luc even though it represented his brother in a recent DUI and firearm case for which he is still on probation.

Brian Luc was also arrested Sunday on suspicion of narcotics possession, being a felon in possession of ammunition and violation of his probation.

The Public Defender’s Office said it would appeal the ruling. In the meantime, Binh’s defense has been turned over to Mark Goldrosen, a defense lawyer with experience in special circumstance cases.

“I’ve done many homicide cases. I’ve done a number of cases when special circumstances have been alleged. I’ve done, both in federal court and state court, cases in which my clients have been eligible for the death penalty. I’m not sure I’ve ever done one where there have been this many victims,” Goldrosen said outside court.

Luc will be arraigned next week on five counts of murder with special circumstances of committing multiple murders. He also faces charges of robbery, burglary and lying in wait. His prior felony robbery assault conviction also adds another special circumstance to the charges.